Thermal-sensitive device



May 25, 1954 N. o. CLARK THERMAL-SENSITIVE DEVICE Filed April 27, 1951 /6 A? 4 I 4 2g 2 I I l I 5 24 Z2 mmvrox E A) 0.6 ns p 8/: 6 l

9 Q a? as 3 45' 4rrar4 f/ Patented May 25, 1954 UNITED STATES PATENT OFFICE 2,679,566 THERMAL-SENSITIVE DEVICE Nelson 0. Clark, Winthrop, Mass. Application April 27, 1951, Serial No. 223,422

. 6 Claims. (Cl. 200-437) This invention relates broadly to thermal-sensitive devices and in particular to such devices which are intended to be unaffected by gradual temperature changes in the ambient temperature to which these devices are normally exposed, but to react quickly in response to relatively sudden changes in temperature.

The device of the present invention is not to be confused with well known thermostatic de vices used for regulating temperature within certain limits, since it operates on an entirely diiierent principle. Broadly speaking, the present invention contemplates the employment of a relatively massive, substantially inert body in combination with a highly sensitive, relatively gradual changes 01 the ambient temperature surrounding the device.

Another object 0! this invention is the provision of a relatively simple, highly-eflicient and substantially inexpensive device of the type indicated, the rate of operation of which device may be readily controlled.

A more specific object of this invention is the provision oi a thermal-sensitive device wherein is employed at least one relatively massive or voluminous, substantially inert body and a relatively lightweight, thin diaphragm exposed to lightweight body, and wherein the massive body thermalsensitive diaphragm or disc, which is slightly bowed and which is held under tension body, and from which body the diaphragm is electrically insulated. Within the body there is provided a contact which is rendered adjustable relative to said diaphragm and is adapted to be engaged by the latter. By the adjustment of the contact the rate of speed or the time required for effecting either the engagement of the contact by the diaphragm or the latters disengagement from the contact is determined. It is preferred that both the massive body as well as the diaphragm are made of material having substantially equal or nearly equal coefficients of thermal expansion. In order to adapt the device for practical use as an electric control instrumerit, the contact of the body and the diaphragm or that portion thereof adapted to engage the contact are provided with independent conductors leading to the circuit to be controlled by the device.

Although it is preferred to construct the masquick reception of temperature changes in the ambient temperature to which the device is exposed, said diaphragm being highly sensitive, andbeing adapted to quickly react to such changes induced either by radiation or convection, and wherein the massive body employed is preferably protected against such quick changes in the ambient temperature and due to its relatively large volume possesses a greater heat-retaining capacity than said diaphragmand therefore is intended to lag behind in responding to sudden changes in the ambient temperature, such lag may be determined to be in definite proportion or rate in respect to the action of the diaphragm and which action or rate of action may b determined by adjustment means with which' e device is equipped.

Still another specific object of this invention is the provision of a device for the purpose indicated, which consists of a relatively voluminous body in conjunction with a lightweight, relatively thin diaphragm rendered operative in respect to said body, and wherein the body is so constructed that it is adapted to receive a dielectric peripheral holder for thatdiaphragm so that the latter is kept under compression or tensional stress, and wherein means are provided for fixedly joining the holder, gripping the diaphragm, with said voluminous body, the latter being equipped with an adjustable contact which is intended for engagement by said diaphragm, and wherein independent electric conductors are connected with the diaphragm and said body and lead outward from the device to whatever instrumentality is to be regulated by the latter.

A still further object of this invention is the provision of the device as stated above, and wherein, for the purpose of increasing the sensitiveness of the diaphragm, a heating element is incorporated in the device which is adapted to raise the temperature of the diaphragm and thus placing the diaphragm under greater tension above that normally exerted by its holder.

Another object of this invention is the prothat diaphragm is bowed outwardly in respect to the voluminous body and is held under tension bya dielectric holder lodged in the body, the diaphragm being adapted to normally engage said adjustable contact and being further adapted to disengage that contact when a sudden rise in temperature occurs.

Still another object 01' this inventionis the provision of a device of the type indicated, employing a relatively voluminous body in conjunction with a thin bowed diaphragm, said body having an adtowards. said body and is held under tension within a dielectric holder lodged in the body and is adapted to normally clear the contact in the body, but being further adapted to engage the contact in response to' sudden temperature changes in the ambient temperature surrounding the device.

A still furtherobject of this invention is the provision of a thermal-sensitive device wherein is employed at least one substantially voluminous inert body in conjunction with two diaphragms, one being bowed outwardly in respect to the body, the other being bowed toward the body, both diaphragms being held under tension and being dielectrically insulated from the body, and wherein the body is provided with two adjustable contacts adapted to be engaged by the two diaphragms, and wherein independent electric conductors lead from each one of the diaphragms and from the body to an instrument to be controlled by the actionof the device, the device being adapted to serve as a double throw switch foreither first breaking the circuit before making it, or for first closing the circuit before breaking it. i i

The foregoing and numerous other objects and important advantages of this invention will become more clearly evident as the description of the device progresses in conjunction with the accompanying drawings, disclosing several embodiments of the invention in the presently preferred form, but which illustrations are by no means intended to restrict the invention to the actual structures shown, and wherein:

Fig. 1 is a vertical section through one form of the device;

Fig. 2 is a section in reduced size taken along line 2-2 of Fig. 1;

Fig. 3 is a bottom view, also in reduced size, of the device shown in Fig. 1;

Fig. 4 is a vertical section through a modified form of the device similar to that shown in Fig. 1;

- and Fig. 5 is a vertical section through still another modification of the device for use as a switch with a double throw action.

The device shown in Figs. 1, 2 and 3 comprises a relatively massive or voluminous body III; which is dished or recessed as at II, to provide a seat for the reception of a dielectric clamping ring i2,

' preferably composed of three or more sections l 3,

clearly seen in Fig. 2, although a peripherally adjustable ring, such as a simple split ring will serve the purpose. Ring 12 has an internal, sub-- stantially V-shaped seating groove I4 in which is held under tension or compression a bowed, relatively thin diaphragm I5 which is substantially less massive or less voluminous than body II). It ispreferred that a contact point, such as contact I 6, be secured at or'near the apex'of diaphragm I5, although its use is not absolutely essential. Ring I2 is adapted to hold diaphragm I5 under tension or compression stress and, being peripherally adjustable, facilitates its being forcibly seated in recess H of body l0, and thus exert pressure peripherally toward the apex of the diaphragm. Passing through body In is an adjusting screw I I, preferably equipped with a contact I8 for engagement by contact I6 of the diaphragm. A look nut IQ for the adjustable contact screw I1 is illustrated but is not absolutely essential. Connected with the diaphragm is an electric conductor 20 and another conductor 2I extends from body I0. Aninsulating disc 22 is placed against the bottom of body III and ad-' jacent disc 22- there is a mounting plate 23, preferably of rigid metal, said plate having mounting holes 23. 'Exteriorly to body I0, as well as to insulating disc 22 and mounting plate 23, there is provided an insulation sleeve 24. Engaging the seating ring in the recess I I of body Ill and firmly connecting the ring, the body, insulating disc 22 and mounting plate 23, and holding all of these elements in fixed relation to one another is an outer metal casing or housing 25. It will be noted that lead 20 from diaphragm l5 passes through I an insulation tubing 26.

As an optional feature intended for the device there will be seen a resistance heater 21, the independent leads 28 of whichpass through insulating cylinders 29 seated in body I0. Heating element 21, when energized, is adapted to heat diaphragm I5, thereby increasing the tension at which the diaphragm is normally held by ring I 2, thus augmenting the sensitiveness of the diaphragm and shortening the time of its reaction to sudden temperature changes.

A modified form of the above-described device is illustrated in Fig. 4 wherein again a relatively voluminous body In is illustrated, which holds in its recessed seat I I peripherally adjustable clamping ring I2, the latter being again provided with av-shaped groove I4 in which is tensionaily held diaphragm I5, bowed inwardly, that is toward body III. The diaphragm is shown equipped with a contact I6 opposite an adjustable contact screw ll, having a contact I8. Engaging the screw is an adjusting nut I9. An electric conductor 20' extends from diaphragm I5 through body I0, and lead 2| serves for connection from the body. Insulating disc 22, mounting plate 23 equipped with mounting holes 23', insulating sleeve 24 and housing 25 holding all the elements of the device in fixed relation to each other are again employed,

the same as in Fig. 1. Contact I6 of diaphragm I5 are adapted in this second embodiment to be normally spaced from adjustable contact screw II.

In the modification illustrated in Fig. 5 there is again employed a substantially inert, voluminous body 30, provided with oppositely disposed seating recesses 3| and 32, in which are lodged clamping rings 33 and 34 for outwardly and inwardly bowed diaphragms 35 and 36, respectively. In the body 30 there are mounted adjustable contact screws 31 and 38 adapted for engagement by their respective diaphragms. These diaphragms are preferably equipped with contacts 35' and 36', and in each of the diaphragms there are apertures 39 and for facilitating the ad- Justm'ents of screws 38 and 31 having end contacts. Extending from diaphragm 35 is an insulated lead ll and another such lead 42 electrically connects diaphragm 35. A third lead 43 passes from body 30 through an insulating bead ll of diaphragm 36. It will be noted that in this modification the mounting plate and the insulating disc employed in Figs. 1 and 4 are invention to the specific designs illustrated, since the organization and arrangement of the device is subject to changes arising from the possibility of employing the device as a control for a great number of different instrumentalities adapted to serve a large variety of purposes. 1

Application is by no means to be considered as limiting this When used as a fire-detecting control, the devicemay be held in its simplest form such as shown in Figs. 1 and 4'. Similarly devices of such construction may be used as controls to prevent overriding of heating systems due to sudden changes in outdoor temperatureror for the protection of industrial furnaces and similar equipment which may be damaged by sudden changes in temperature. Either of the devices shown in Figs. 1 and 4 or the modified form illustrated in Fig. 5 may be employed as a control for heat treating equipment, or as a sentinel during the cooling period after heat treatment. The above are only a few examples ofpossible employment to indicate the versatility of thepresent device, which may he obviously used as a control for any instrumentality or any system where it is essential to prevent either over-function, or under-function of such a system and to anticipate or prevent them, when a temporary or sudden, temperature change occurs.

' Basic function It is assumed that the device is exposed to normalambient temperature. When, due to sudden or temporary conditions, changes in temperature take place, such rapid changes in temperature will not affect the rather voluminous body of the device, such as bodies l0 and 30, but will immediately cause the operation of diaphragms l5, I5, and 36, which, due to their being held constantly under stress or tension, become extremely sensitive, and will immediately react to such sudden temperature changes.

In the embodiment shown in Fig; 1, diaphragm [5, when exposed to a rapid increase in temperature, will expand and will disengage, adjustable contact ll. In the form shown in Fig.4 diaphragm l5' will also expand in response to such sudden temperature changes and will move to engage contact H.

In the modification shown in Fig. 5 diaphragm 35, when exposed to a sudden rise of heat, will disengage contact 31 while diaphragm 38 will move into engagement with contact 38.

One of the noteworthy features of the present device resides in the fact that the massive or voluminous inert bodies in all modifications illus-' trated are covered to shield them more or less against direct exposure to sudden temperature changes whereas the diaphragms are fully exposed. In Figs. 1 and 4 seating ring I2, housing 25, insulating sleeve 24, mounting plate 23 and insulating disc 22 fulfill together with diaphragms I5 and IS the function of shielding body I 0; in

the form shown in Fig. 5 the shielding function is effected by rings '33, 34, insulated housing and the two diaphragms 35 and 36.

When changes in the ambient temperature are radual over a relatively long period of time, the entire device will so-to-speak accommodate itself to such changes, and the diaphragms will not.

operate in respect to their contacts. Thus only when sudden temporary changes in temperature take place. action by the diaphragms is intended.

The three modifications illustrated are designed to react to upward changes in temperature.

Obviously they may be adapted for downward fluctuation in temperature by suitably shaping the diaphragms to respond to sudden lowering of the ambient temperature to which the devices are exposed. Such changes in the construction of the diaphragms being self-evident, specific illustrations of devices responsive to downward fluctuations in the ambient temperature have been omitted.

Therefore, while the preceding description explains the construction of the specific illustraerate with said body and operatively mounted within the dished portion thereof and being readily responsive to sudden temperature changes, and insulation material intimately associated with and substantially completely covering all outer surfaces of said body except those adjacent said diaphragm.

2. In a thermal-sensitive device according to claim 1, and wherein said body forms an annulus, and wherein said body and said diaphragm are made of a material having a substantially equal coefiicient of thermal expansion, and wherein a part of said insulation material forms a ring within the dished. portion of the body, and wherein said diaphragm is mounted within said ring.

3. In a thermal-sensitive device according to claim 2, and wherein said ring has an annular recess at its interior periphery for accommodating said diaphragm and for holding the latter under compression.

4. In a thermal-sensitive" device according-to claim 3, and wherein fixed contact means are provided with said diaphragm and adjustable con tact means are provided within said body, the latter contact means being adapted to cooperate with and being movable relative to said fixed coni tact means.

5. In a thermal-sensitive device according to claim 4, and wherein a casing is provided to enclose said massive body. and to engage said of said contact means in respect to said diaphragm ing the diaphragm held in said seat, said diadiaphragm-holding ring so that said adjustable a contact means are rendered accessible.

6. In a thermal-sensitive switch device, the combination with a relatively massive shielded metal body, of relatively thin exposed metal diaphragm highly sensitive and readily responsive to sudden changes in ambient temperature to which latter the device is normally exposed, said diaphragm being operative in respect to said body, adjustable contact means extending from the body, said diaphragm being adapted for cooperation with said contact means; the adjustment phragm and said body being insulated from one another, and a housing for and insulated from said diaphragm and said body for holding these two elements in fixedrelation to one another.

References Cited in the file of this patent] UNITED STATES PATENTS Bower Sept. lg i945 

